Medical image diagnoses have been rapidly progressing as computers have been improved since 1970's. The medical image diagnoses are accomplished by, for example, an X-ray diagnosis apparatus, an magnetic resonance imaging (MRI) apparatus, an X-ray computed tomography (CT) apparatus, or the like. Nowadays such diagnoses play a very important role for the medical practice. Medical images obtained by medical image equipments, such as those mentioned above, are usually observed and interpreted by a doctor or the like in his or her medical image diagnosis. In addition, the medical images may also be used, as a part of the diagnosis, for measuring a predetermined part of a patient's body, such as a organ and a bone. In a diagnosis of scoliosis as an example of bones diagnoses, a bow scale of the spine is calculated based on transmission images obtained in an X-ray diagnosis apparatus. It is said that scoliosis may occur when a spinal cord grows faster than its peripheral organs. Scoliosis tends to appear particularly in adolescent children who, therefore, are required a once-a-month follow-up.
FIG. 1 is an illustration showing examples of measuring techniques of a bow scale in a diagnosis of scoliosis according to a prior art of the present invention. FIG. 1(A) shows a measurement of the Cobb angles on a radiograph (image) of a patient or an examination object (hereinafter referred to as a specimen) for calculating bow angles. FIG. 1(B) shows a measurement of the ‘Vertical-alignment’ distances on a radiograph (image) of the specimen for calculating deviations from a representative straight line along a spine, which is one as a hypothetically ideal healthy straight spine along a body axis of the specimen (hereinafter referred to as a median line). The median line may therefore be determined to indicate a center of a body axis of the specimen. The bow scale such as, for example, the Cobb angle and the ‘Vertical-alignment’ distance shows how much the spine is bent or curved. Basics of the Cobb angle and the ‘Vertical-alignment’ distance have been established and methods of such measurements are standards known in the art.
In the Cobb angle calculation, as shown in FIG. 1(A), an operator, such as a doctor or a radiological technologist, observes an X-ray transmission image (hereinafter referred to as an image) displayed in a display. The operator then determines by the eye (or determines with his or her sense) one or more points, such as points 1 to 3, which are least bent points of a spine 4 (as long as the operator believes). Each adjacent two least bent points have a most bent point of the spine 4 between the each adjacent two points, based on the displayed image. At the determined points 1 to 3, the operator manually draws perpendicular lines 5 to 7 perpendicular to tangent lines 8 to 10, respectively, using, for example, a mouse. In detail, the operator determines the point 1, and draws the tangent line 8 at the point 1. Further, the operator draws the perpendicular line 5 perpendicular to the tangent line 8. Similarly, the operator draws the perpendicular line 6 perpendicular to the tangent line 9 drawn at the determined point 2. Still further, the operator draws the perpendicular line 7 perpendicular to the tangent line 10 drawn at the determined point 3. A medical image processing apparatus connected to the display calculates angles α and β created by the perpendicular lines 5 to 7. Namely, the perpendicular lines 5 and 6 cross with the angle α and similarly the perpendicular lines 6 and 7 cross with the angle β. The calculated angles α and β are displayed in the display.
In the distance calculation of ‘Vertical-alignment’, as shown in FIG. 1(B), the operator observes an image displayed in the display and draws a median line 11 along the spine 4. The median line 11 is guessed and determined by the eye of the operator, based on the displayed image. The median line 11 intersects with the spine 4 at intersection points 12 to 14. Then, the operator determines by the eye points 15 and 16 of the spine 4, each of which is the furthest (as long as the operator believes) from the median line 11 between each two adjacent intersection points of the intersection points 12 to 14 when perpendicular lines are dropped to the median line 11 from the points 15 and 16. In more detail, the operator determines the point 15 which is between the intersection points 12 and 13. Further, the operator determines the point 16 which is between the intersection points 13 and 14. The medical image processing apparatus calculates a distance 17 between the point 15 and the median line 11 when the perpendicular line is dropped to the median line 11 from the point 15. Similarly, the medical image processing apparatus calculates a distance 18 between the point 16 and the median line 11 when the perpendicular line is dropped to the median line 11 from the point 16. The calculated distances 17 and 18 are displayed in the display.
In the prior art, scoliosis has been diagnosed using the calculated angles and/or distances as an index of the bow scale. The Cobb angle and the ‘Vertical-alignment’ distance have been conventionally obtained for the diagnosis of scoliosis based on the points and lines, which were selected and drawn in accordance with the determination by the operator's sense.
Concretely, in the Cobb angle calculation, the points 1 to 3 of the spine 4 in the image displayed in the display were selected based on the operator's sense by observing the image with his or her eyes. Further, the tangent lines 8 to 10 and the perpendicular lines 5 to 7 were drawn based on the operator's sense by observing the image with his or her eyes. Similarly, in the ‘Vertical alignment’ distance calculation, the median line 11 was drawn based on the operator's sense by observing the image with his or her eyes. Further, the points 15 and 16 were selected based on the operator's sense by observing the image with his or her eyes.
Therefore, the selected points and/or the drawn lines are quite subjective and accordingly the calculated result may be likely to be different among operators. Further, even when it is done by the same operator, the same result may not be reproduced if the operator does not have a clear standard for his or her determination of the selection and/or the drawing. Particularly, as mentioned above, the case of scoliosis may require the once-a-month follow-up of the bow scale of the spine. Therefore, the reproducibility should be kept and is a very important factor for the diagnosis of the scoliosis.
One of factors contributing to the difficulty of the reproducibility (or the deterioration of the calculation accuracy) through the human being system may be as follows. The calculation is made for a very limited tiny region compared to the whole image displayed in the display. In addition, the state of bow of the spine is usually subtle and may be sometimes beyond the discrimination of the human beings. Therefore, the accuracy of the measurement result may not be assured in some cases.